1. Field of the Invention
The present invention relates to a method of transmitting an Ethernet frame in a network bridge. More particularly the present invention relates to a method of transmitting a frame using a check-and-forward technique by using a header CRC flag included in a received Ethernet frame and header CRC.
2. Description of the Related Art
Development of computer network technologies for the Internet has lead to the development of technologies for the general information industry. The developed network technologies opens up new vistas of computing technology, such as providing new services that generate added value to wired or wireless connections between computers.
Network technologies have been rapidly developed and now virtually all computers are connected to a network. Ethernet is an essential aspect of the success of network technologies. Ethernet has been used in numerous types of wired/wireless networks, due to its simple structure.
However, despite Ethernet having been applied to broad fields, Ethernet has not been generally used in time-sensitive and real-time streaming applications, due to a limit of being incapable of supporting isochronous services. Due to a rapid increase of interests in high-quality digital audio-video services, the above limit of the Ethernet has increasingly gained attention. Currently, starting with residential Ethernet, research on Ethernet technology for supporting time-sensitive applications is vigorously being pursued.
A network bridge is an apparatus for transmitting an Ethernet frame between nodes mutually connected via a network. A conventional Ethernet network bridge apparatus supports a frame transmission method generally referred to as a store-and-forward technique. The store-and-forward technique has a switching method in which an entire received Ethernet frame is temporarily stored in a buffer and is forwarded to a next node after a process of detecting an error, such as cyclic redundancy check (CRC), is finished.
Since a considerable amount of time is used in receiving and storing an Ethernet frame and a delay at each node is added to an end-to-end delay. Thus, the above switching method is not suitable for the time-sensitive applications.
Conversely, to solve the problem of excessive delays of the store-and-forward technique, when using a cut-through switching technique in which a frame is directly forwarded by referring to a header of a received Ethernet frame, data included in the frame header, such as a destination address, a source address, and a frame type, is not reliable.
Accordingly, a switching method is needed to secure precision of the frame header data while reducing a time delay due to the forwarding of the frame to support a real-time application.
Also, in a future home network to which real-time applications are applied, digital rights management (DRM) for provided content is an important issue. In one implementation of the DRM, repeated use of content with respect to some applications is limited to a local scope, such as residential scope. In this case, a media server of a content provider has to recognize whether a media player of a content receiver is located within a scope of a certain network distance from a sender of data. However, since a conventional Ethernet bridge apparatus does not support a network distance measurement and a time delay at a bridge apparatus forming each node has a great variance depending upon a traffic state, it is difficult to precisely measure.
The present invention provides a network bridge apparatus capable of solving the above problems, effectively supporting time-sensitive and real-time applications, and maintaining compatibility with a conventional Ethernet bridge apparatus.